This system is in the field of coolers for thermal imagers; such coolers may take any one of several forms. For instance, gas-expansion coolers, Peltier effect coolers, and mechanical-compressor refrigerators (such as Sterling cycle) are all used. When such coolers are used for portable equipment, various types of coolers have various advantages. For simplicity, a gas-expansion cooler would seem ideal; however, temperature control of such a cooler is difficult and special equipment and trained operators are required to refill the compressed air bottles usually used with such coolers. Obviously, a mechanical-compressor refrigerator (or another type of electrically-powered cooler) is able to operate only for a limited time on battery power; if the cooler operates continuously, intervals between battery charges or recharges are least. If the cooler is only energized when one desires to view a thermal image, the battery life may be greatly extended, but some time interval must be allowed for the cooler to cool the thermal imager from ambient to cryogenic temperatures. For particular cooler-imager combinations, this interval may be as long as five minutes. In the case where such a combination is being used for military observation or surveilliance, such a reaction time may be unacceptably long. The present invention is able to provide extended battery life for an imager, but without totally sacrificing reaction time.